Roll Stability Cooperative Control Of In-wheel Motors Drive Electric Vehicle In Harsh Road Conditions

The dynamic performance of in-wheel motors driven electric vehicle(IWMDEV)can be greatly improved by adjusting the torque and speed of the in-wheel motors,but the increased unsprung mass due to the in-wheel motors will bring greater dynamic load impact to the body on potholed roads,which may make the vehicle roll over when turning on potholed roads,posing significant challenges to the vehicle control system.A roll stability control method based on the coordination of four-wheel differential drive and active suspension is proposed in order to improve the roll stability of IWMDEV on potholed roads.So as to improve the stability control effect of IWMDEV in harsh road conditions.The key research components of this paper are as follows:(1)Taking the IWMDEV as the research object and considering the actual response characteristics of the in-wheel motors and the tire model applicable to the potholes,the whole vehicle dynamics model is constructed,covering the vehicle power drive system,SWIFT tire model and suspension system.The model simulation results of the vehicle under specific operating conditions are compared with the results of real vehicle tests to verify the accuracy of the developed vehicle dynamics model.(2)The characteristics of the dynamics and spatial instability mechanisms of an IWMDEV rolling over on potholed roads are analyzed.The spatial stability variation law of the vehicle under four-wheel differential drive and active suspension control is next revealed.The coupling mechanism between the above two control methods is clarified through force analysis of the suspension system guide bar system,and the effect of different control methods on vehicle roll stability under typical lateral instability conditions is explored.The additional effect of differential drive control on vehicle roll stability is verified through simulation.(3)A four-wheel differential drive sliding mode variable structure controller,along with an active suspension adaptive robust sliding mode controller,are combined to create a roll stability cooperative controller.Based on the sliding mode control theory and the hierarchical control concept,the upper-level controller determines the desired output.The timing of the active suspension control intervention and the yaw and roll moment distribution strategy are then developed while taking into account the impact of lateral load transfer on the tire cornering stiffness.The effect of the cooperative control strategy for roll stability proposed in this paper on the suppression of excessive body roll and yaw is verified through simulation.(4)Real vehicle tests were conducted on the effectiveness of differential drive control in stabilizing a vehicle’s roll and yaw using an IWMDEV test vehicle,a d SPACE real-time simulation system,and several onboard sensors.During the test,front-wheel and four-wheel differential drive control were performed,respectively,and the data from the real vehicle test results were collected and analyzed.The results indicate that differential drive control can effectively reduce the vehicle’s roll angle and yaw rate.When only the front axle’s two-wheel differential drive control is used,the suppression effect on body roll is more obvious than with the four-wheel differential drive control.